1. Technical Field
The present invention relates to a green tire and a method for manufacturing a pneumatic tire, the green tire having a surface layer defining a part of the green tire surface by a rubber tape laminate circumferentially wound on the green tire.
2. Related Art
A recently proposed pneumatic tire has its various rubber members, such as tread rubber, side wall rubber, and inner liner rubber, formed of a tape laminate that is made up of an unvulcanized rubber tape circumferentially wound on the tire. The idea of winding eliminates the need for a large rubber extruder and thus enables plant equipment to be miniaturized. Also there is no troublesome work conventionally required on every occasion when there was a change in kind of the tires to be manufactured, such as nozzle replacement for the rubber extruder and adjustments. Thus, the idea of winding can be highly advantageous for tires manufactured in a wide variety of kinds but in small quantities.
However, as shown in FIG. 12, a rubber member “a” formed by winding is weak in strength even after vulcanization at an interface J between adjacent windings g of the rubber tape, so that the interface J is exposed on the surface of the rubber member “a”. In the case of the rubber member “a” being, for example, a side wall rubber a1, which is largely distorted on the surface during tire deformation, an exposed point Jp of the interface J serves as a starting point of cracking, thus posing the problem of degraded tire durability.
In view of this, a technique to inhibit cracking is disclosed in, for example, Japanese unexamined Patent Application Publication No. 2005-225278. This technique decreases the number of exposed points on the tire surface by forming the side wall rubber a1 of an inner layer with larger overlapping widths of the rubber tape and a surface layer with smaller overlapping widths. However, a study conducted by the present inventors has revealed that cracking is difficult to inhibit on a sufficient level only by a decrease in the number of exposed points, especially in the case of running under the severe conditions of low internal pressure and overload.
Pneumatic tires include what is called self-supporting run-flat tires, which are known to enable the vehicle to be driven safely over some distances at relatively high speeds even when the air within the tire is greatly reduced because of puncture and the like. The run-flat tire is provided with a side reinforcing rubber substantially in the form of a crescent on the inner cavity side of the side wall portion. Recently, an attempt is being made to form the side reinforcing rubber of a tape laminate. However, even the run-flat tire is largely deformed during the run-flat occasion, which excessively distorts the inner surface (inner cavity surface) of the side reinforcing rubber. Thus, cracking on the side reinforcing rubber is difficult to inhibit on a sufficient level by the technique disclosed in the JP2005-225278 publication. Thus, there is a need for further improvement in winding.